Synthesis Of CdS/Organic Nano-composite And Study Of Their Photoluminescence Properties

In all of the optoelectronic materials, CdS was paid more attention for the excellent properties, which has commercial and potential applications in light-emitting diodes, solar cells, and other optoelectronic devices. Its band gap is 2.42eV at room temperature. CdS nanoparticles show significant quantum-size effect when their sizes are smaller than 6nm. There have been many attempts to obtain narrow size distribution and good optical properties of CdS nanoparticles and make them stable under normal atmospheric. The thesis has summed up the synthesis methods of organic/CdS nanoparticles composite, CdS nanowires and their applications.According to the problems in current research, my works have four parts as following:1. CdS nanoparticles were synthesized by surface-modified with thiourea and stabilized by poly (N-vinyl-2-pyrrolidone) (PVP). The results showed that CdS nanoparticles, which exhibited significantly quantum size effect and enhanced luminescence, were prepared through the surface modified with thiourea. The FT-IR spectra of the surface-modified CdS nanoparticles showed that the atom of S in thethiourea could effectively chelated with Cd , which prevented S " from reacting with Cd2+. The UV-Vis spectra results indicated that the optical properties of CdS nanoparticles were depended on the reactive conditions. After CdS was modified by thiourea, the enhanced luminescence was observed.2. In order to improve the luminescence properties, CdS nanoparticles entrapped in an Acrylic acid-hydroxypropyl acrylate copolymer (AC-HAC) network were synthesized by in-situ synthesis method. AC-HAC is a kind of polymer, which has strong chelation ability with Cd2+ because of its carboxyl group. The chelation ability made AC-HAC act as a protection layer on the surface of CdS nanoparticles, which reduced surface states and improved the band edge emission.3. By solvothermal method, CdS nanoparticles with various sizes and shapes were synthesized using different ratios of ethylenediamine to water. The results revealed that CdS nanorods were formed by using ethylenediamine and the mixture of ethylenediamine and water as solvents. The CdS nanorods were about 12-20nm wide and 50-300nm long when absolute ethylenediamine was used as solvent. When the mixture of ethylenediamine and water as solvents, the size, morphology andphotoluminescence feature of CdS particles could be adjusted by changing the ratios of ethylenediamine to water. When water was added into the system, the reciprocity of water and ethylenediamine prevented ethylenediamine from coordinating with Cd2+, and then shorter CdS nanorods formed.4. CdS nanowires were synthesized by the solvothermal reaction of Cd2+-dispersed poly vinyl-alcohol (PVA) with ethylenediamine as reaction medium. The structure and optical properties of CdS nanowires were characterized. The formation mechanism of CdS nanowires was also discussed. Only short CdS nanorods with low aspect ratio were obtained in the case of only using ethylenediamine as the reaction medium. Compared with the sample prepared without PVA, the CdS nanowires synthesized using PVA as matrix showed longer length and higher aspect ratio. TEM images showed the typical wire-like morphology with widths of about 10-20nm and lengths up to about 6um. UV-Vis absorption spectra and PL spectra of the obtained CdS nanowires indicated the characteristic of the bulk CdS.